1. Field of the Invention
The invention relates in general, to gas-operated firearms. More particularly, the present invention relates to the buffer system and buttstocks of autoloading firearms in the AR15/M16/M4 series of firearms.
2. Description of the Related Art
Militaries worldwide rely on a variety of firearms for both defensive and offensive purposes. In general, these firearms are divided into various subcategories based on the firearms structural features and the ammunition type used. Example categories include, but are not limited to, handguns, submachine guns and rifles. All three listed categories of weapons are often issued as the primary individual weapon for soldiers or police forces, based on the task the user is expected to perform.
Handguns and submachine guns are selected because they are light and compact. Their diminutive size allows for easy transportation, deployment and use within a vehicle while their weight makes them ideal for daily carry. The submachine gun, while being slightly more obtrusive than the handgun, increases the firepower and hit probability of the user. Hit probability is primarily increased due to the user having three points of contact with the weapon, compared to only having two points of contact as is the case with a handgun.
The buttstock present on many submachine guns offers a unique point of contact between the user and the firearm, a well known advantage. Handguns and submachine guns fire ammunition cartridges typically associated with handguns, so called pistol ammunition. Handgun cartridges such as 9 mm, .40S&W and 45ACP offer acceptable terminal performance when compared against many other handgun cartridges, but offer poor performance when measured against typical rifle cartridges such as 5.56×45 mm (5.56 mm) and 7.62×51 mm (7.62 mm) ammunition. Additionally, a handgun's optimal performance range is 25-50 yards while a submachine gun using similar ammunition may extend the effective range of the cartridges out to 100-150 yards. The effective range is dependent on which specific handgun cartridge is being used. It must be noted that while a handgun cartridge being fired from a submachine gun may have an effective range up to 150 yards, meaning it is capable of sufficiently penetrating the target, it will generally have poor terminal performance on the intended target at that range.
This poor terminal performance is because most defensive handgun ammunition uses hollow point bullet construction, or other expanding design, which will not expand consistently past 25-50 yards due to a lack of velocity. Handgun ammunition is also generally deficient in penetrating intermediate barriers such as wood, auto bodies and laminate glass while at the same time remaining terminally effective at all but the closest ranges, i.e. 25 yards and less.
The next class of firearms is rifles, a class often subdivided into carbines and rifles based on barrel length and other characteristics of the firearm. For the purpose of this disclosure the term “rifle” will include carbines unless otherwise noted. Rifles are the primary armament of militaries worldwide. An example rifle would be the M16/M4 family of firearms and many of its derivatives such as the M6 piston driven design produced by LWRC International. Rifles typically have an effective range exceeding 600 yards. Rifle cartridges such as the 5.56 mm and 7.62 mm offer drastically increased intermediate barrier penetration, terminal performance, and superior external ballistics characteristics when compared to any handgun cartridge. The down side to a rifle is typically its overall length and to a lesser extent, its weight. Size restrictions make it difficult for tank and aircraft crews for example, to carry a rifle. This often leaves people confined to tight quarters armed with submachine guns at best, or pistols at worst. Should these crews be required to deploy their weapons in a violent confrontation they will immediately be disadvantaged when confronted by enemy forces equipped with rifles, to include the ubiquitous AK47 frequently used by enemy forces. As such, there is a persistent need to provide a firearm which offers the terminal and external ballistics, and intermediate barrier penetration capabilities of a rifle but in a package which is no larger than a submachine gun.
Attempts to provide a firearm which has the compact size of a submachine gun, capable of firing ammunition with terminal and external ballistic similar to a rifle have been made. Many of these designs are referred to as Personal Defense Weapons (PDW). Designs which try to incorporate all of these features have been around for many years. Many previous attempts to produce a PDW failed because the design relied on a proprietary ammunition cartridge, was insufficiently compact, non-ergonomic, or simply unreliable. It should be noted that PDWs for the purpose of this disclosure only includes those designs which are capable of firing what is generally considered rifle ammunition. PDW designs which fire handgun ammunition such as 9×19 mm, .40S&W, .45ACP, FN 5.7 mm and HK 4.6 mm ammunition generally rely on operating systems which are not capable of firing traditional rifle ammunition. Further, such rounds do not have external or terminal ballistic characteristics comparable to conventional rifle ammunition and are not capable of satisfying the needs of many military and law enforcement end users.
Without being an exhaustive list, the following U.S. Patents disclose various features which are of importance for understanding the improvements provided by the invention as set forth herein. Neither of the two patents mentioned below are admitted to be prior art by the Applicant.
U.S. Pat. No. 5,827,992 to Harris et al (Harris) has several inherent deficiencies in its design that are evidenced by the fact that it never experienced wide acceptance or adoption by any military or police forces. First among these is that the design relies on the use of a new cartridge, the 5.56×30 mm MARS as taught by Harris (see column 9, lines 29-62). Militaries and police forces are slow and often reluctant to adopt new proprietary cartridges due to logistics concerns, unknown terminal performance and cost. Second, Harris does not teach how to make an M16 type rifle capable of firing rifle ammunition that is sufficiently compact to meet the needs of modern end users. In particular, the buffer system so disclosed would not provide for an M16 type weapon having an overall length of 20″ or less when equipped with an 8″ barrel, a requirement for some government contracts. Third, to practice the invention as taught requires the production of a M16 type receiver which dimensionally deviates from the prior art. This would substantially increase the implementation cost of adopting such a design.
U.S. Pat. No. 7,137,217 to Olson and Knight discloses a compact rifle design which relies on an entirely new gas operating system and ammunition cartridge. The proprietary nature of this new firearm, its ergonomics and operating system, and the unique ammunition it uses greatly diminishes the likelihood of its adoption by military or other government forces.
Among military and police forces of the Western world, the AR15/M16 family of firearms and their derivatives, including indirect gas operated versions (piston designs), have been in use for many years. Western nations have trained millions of individuals in the use of these firearms, therefore creating a weapon based on the AR15/M16 design is desirable as the deployment cost resulting from the adoption of a modified weapon system based on the AR15/M16 will be minimal. In addition, designing a new compact weapon system which uses conventional rifle ammunition further reduces deployment cost and logistics concerns.
Compact personal defense weapons based on the AR15/M16 family of firearms are prevalent throughout the prior art. The primary method of reducing the overall length of the rifle has been to reduce the length of the barrel and gas operating system. While this is a valid method of reducing overall length it is not without shortcomings. First, the barrel may only be shortened so much before the external and terminal ballistics characteristics of a rifle projectile are diminished. Second, the shortened barrel reduces dwell time, which is critical to the proper firing cycle of the host rifle. Dwell time is the time between the projectile passing a barrels gas port and when it exits the muzzle of the firearm. This is an important component to the proper function of the firearm. Third, the increased gas pressure generated by many of the prior art rifle designs results in a phenomenon known as bolt bounce. Bolt bounce occurs when the bolt carrier of an AR15/M16 rifle reciprocates so violently that upon its forward movement the bolt carrier bounces back from the chamber end of the barrel. This results in the bolt unlocking from the chamber extension and the bolt carrier absorbing a significant amount of the hammer's force, resulting in a failure to fire. To combat bolt bounce, numerous buffers have been designed that work with varying degrees of success.
Even with a barrel of reduced length, the overall length of the AR15/M16 family of firearms is still restricted by the length of the prior art buffer tube, which is nearly ubiquitous throughout the art.
Shown in FIG. 1A is the prior art carbine buffer assembly used with the AR15/M16 family of firearms. The buffer assembly 300 includes a carbine length buffer tube 330, spring 340, bolt carrier 310, bolt 311 and buffer 320. The rear end of the bolt carrier 310 abuts the front of the buffer 320 when the host rifle is fully assembled. The buffer 320 is contained within the buffer tube 330 and the bolt carrier 310 within an upper receiver when in battery. The bolt carrier 310 (6.672″ long) and buffer 320 (3.245″ long) have a combined length of over 9.9″. While the carbine buffer tube 330 does not receive the entire length of the bolt carrier 310 during its reciprocating motion, the 7.19″ length of the prior art carbine buffer tube is required to facilitate sufficient rearward movement of the bolt carrier 310 and compression of the spring 340 for proper function of the host firearm. The spring 340 and buffer 320 are required to provide a surface and force which resists the rearward movement of the bolt carrier 310. The weight of the buffer 320 is selected to minimize bolt bounce and assist in the proper operation of the gas operating system. As a result, the prior art carbine buffer assembly 300 adds a fixed amount of additional length to AR15/M16 type firearms so equipped.
Therefore in consideration of what is available in the prior art, it would be desirable to have a PDW that uses conventional rifle ammunition, has a barrel long enough to provide terminal and external ballistic similar to a rifle and has an overall length similar to a submachine gun. Additionally, it would be desirable to incorporate the above features onto a firearm having minimal structural and operational differences as compared to the prior art M16/M4 family of firearms.